I. Field
The following relates generally to wireless communication, and more specifically to coding and decoding dedicated reference signals for improved wireless communications.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content and services such as, e.g., voice content, data content, video content, packet data services, broadcast services, messaging services, multimedia services, and so on. Typical wireless communication systems can be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access systems can include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple mobile devices. Each mobile device can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Further, communications between mobile devices and base stations can be established via a single-in-single-out (SISO) system, a multiple-in-single-out (MISO) system, or a multiple-in-multiple-out (MIMO) system.
To facilitate wireless communications, a wireless base station can transmit a reference signal to terminals operating within a wireless communication system. The reference signal comprises coding sequences employed to randomize transmitted symbols, reducing noise and interference among concurrent transmissions in the wireless communication system. Furthermore, terminals can employ these reference signal sequences to decode the transmitted symbols. Thus, upon first entering the wireless system, a terminal will typically analyze received wireless signals to obtain reference signals that contain the coding/decoding information.
In modern wireless communication systems, a base station may transmit general reference signals for use by most or all terminals served by the base station, as well as dedicated reference signals for particular communication content, particular wireless services, or even specific sets of terminals or individual terminals. Additionally, where the base station has multiple antennas (e.g., a MIMO system or directional beamforming system), each antenna can employ a set of reference signals to serve a set of terminals. Thus, a single wireless service area can have concurrent transmission of many reference signals, from one or more sources.
To mitigate noise and interference between reference signals, coding sequences can be used to allocate reference signal symbols to distinct resources of a wireless channel. However, as a number of reference signals in a cell increases, a sufficient number of conventional codes may not exist to distinguish each reference. Additionally, mobile terminals operating in a system may require reference signal codes to be pre-programmed in software or firmware on the device. Accordingly, addition of new coding schemes in a system can prove restrictive for legacy terminals. Thus, it would be desirable for a reference signal coding scheme that mitigates at least the foregoing shortcomings.